1. Field of the Invention
The present invention relates to an electronic circuit module component equipped with an electronic component.
2. Related Background Art
It has been required for electronic components to become further smaller in size as electronic devices to be mounted therewith have been attaining higher performances and smaller sizes. When mounting such an electronic component to a board of an electronic instrument, a terminal electrode of an electronic circuit module component and a pad on the board of the electronic instrument are joined to each other with solder. That is, the electronic circuit module component herein is constituted by a plurality of electronic components mounted to a board with solder so as to have a group of functions. The electronic components made smaller in size have further been demanded to be mounted to printed wiring boards and the like at higher density with solder in a reflow step (a step of placing the electronic components on a board coated beforehand with a solder paste and collectively performing soldering in a continuous furnace), so as to be used as electronic circuit modules in electronic devices and the like.
FIG. 1 is a schematic view of a cross section of an electronic circuit module in which a typical electronic component is mounted on a printed wiring board 10. In this electronic component 1, inner electrode layers 3 are stacked alternately with ceramic layers 4 within an element main body 2 (hereinafter referred to as element body 2). Foundation electrode layers 5 of terminal electrodes 7 are formed so as to cover surfaces of the element body 2 where the inner electrode layers 3 are exposed. The foundation electrode layer 5 has an outer surface formed with a Ni plating layer 6a which, together with a Sn plating layer 6b formed thereon, constitutes a two-layered plating layer 6.
Further, the electronic component 1 is joined through solder 8 to pads 9 on the printed wiring board 10. Heat treatment in the reflow step causes the solder 8 to run the Sn plating layers 6b and wet the surfaces of the plating layers 6, so as to form an intermetallic compound with the Sn plating layers 6b, thereby joining with the pads 9 on the board, thus forming the electronic circuit module component. Examples of such electronic circuit module components have been proposed in Patent Literature 1 (Japanese Patent Application Laid-Open No. 2004-186502) and the like.
On the other hand, as terminal electrodes of electronic components, those of LGA (Land Grid Array) type may be employed in order to be mounted on printed wiring boards and the like at high density with solder. FIG. 2 is a schematic view of a cross section of a typical electronic component employing the LGA for its terminal electrodes.
The electronic component 11 illustrated in FIG. 2 has a plurality of patterns of ceramic layers 13 and inner electrode layers 12 stacked alternately with each other with the inner electrode layers 12 shifting alternately to one side or the other and connecting with their corresponding through-hole electrodes 14 penetrating therethrough in the stacking direction at the shifted parts. Outer connection electrodes 15 are formed as terminal electrodes at respective end parts of the through-hole electrodes 14 and arranged so as to be connectable to a board or the like on one surface of the electronic component 11. Examples of such electronic component 11 equipped with LGA type terminal electrodes have been proposed in Patent Literature 2 (Japanese Patent Application Laid-Open No. 2010-045209) and the like.
In the electronic component 1, however, the terminal electrodes 7 are formed on the lower face of the element body 2 (the surface opposing the printed wiring board 10; hereinafter referred to as mounting surface) and side faces of the element body 2 adjacent to the mounting surface. At the time of soldering, the solder wets not only the surfaces of the mounting parts of the terminal electrodes 7 formed on the mounting surface of the element body 2, but also surfaces of the side faces which abut the surfaces of the mounting parts of the terminal electrodes 7, which makes it difficult for the mounting area to become smaller on the printed wiring board 10. In the case of an electronic circuit module component mounted on a board such that electronic components have a very small distance therebetween, the gap between the side face parts of the terminal electrodes of the electronic components may be so narrow that unnecessary substances such as dust entering there is likely to induce a problem such as a short circuit therethrough, which puts a limit to increasing the density of electronic components in the electronic circuit module component.
In the electronic component 11, on the other hand, terminal electrode parts can be formed as the outer connection electrodes 15 on the lower face alone, which makes it easier to reduce the mounting area. However, it necessitates complicated steps of making through-holes, filling the through-holes with conductive pastes, and so forth at the time of forming the electronic component 11, which makes it hard to further thin the ceramic layers 13 and inner electrode layers 12 or increase the number thereof. The existence of the through-hole electrodes 14 makes the effective electrode area smaller than that of the conventional electronic component 1, thereby making it harder to produce an electronic component having a large capacity. Hence, there has been a limit to reducing the mounting area, which has been advancing together with demands for making these electronic components smaller, whereby it has been required to reduce the mounting area without lowering the capacity of the electronic component.